PIP4Ks impact on PI3K, FOXP3, and UHRF1 signaling and modulate human regulatory T cell proliferation and immunosuppressive activity

Abstract

Regulatory T cells (Tregs) play fundamental roles in maintaining peripheral tolerance to prevent autoimmunity and limit legitimate immune responses, a feature hijacked in tumor microenvironments in which the recruitment of Tregs often extinguishes immune surveillance through suppression of T-effector cell signaling and tumor cell killing. The pharmacological tuning of Treg activity without impacting on T conventional (Tconv) cell activity would likely be beneficial in the treatment of various human pathologies. PIP4K2A, 2B, and 2C constitute a family of lipid kinases that phosphorylate PtdIns5P to PtdIns(4,5)P2. They are involved in stress signaling, act as synthetic lethal targets in p53-null tumors, and in mice, the loss of PIP4K2C leads to late onset hyperinflammation. Accordingly, a human single nucleotide polymorphism (SNP) near the PIP4K2C gene is linked with susceptibility to autoimmune diseases. How PIP4Ks impact on human T cell signaling is not known. Using ex vivo human primary T cells, we found that PIP4K activity is required for Treg cell signaling and immunosuppressive activity. Genetic and pharmacological inhibition of PIP4K in Tregs reduces signaling through the PI3K, mTORC1/S6, and MAPK pathways, impairs cell proliferation, and increases activation-induced cell death while sparing Tconv. PIP4K and PI3K signaling regulate the expression of the Treg master transcriptional activator FOXP3 and the epigenetic signaling protein Ubiquitin-like containing PHD and RING finger domains 1 (UHRF1). Our studies suggest that the pharmacological inhibition of PIP4K can reprogram human Treg identity while leaving Tconv cell signaling and T-helper differentiation to largely intact potentially enhancing overall immunological activity.

PIP4K2B is a mechanosensor and induces heterochromatin-driven nuclear softening through UHRF1

“…The binding with this lipid second messenger allosterically regulates UHRF1 protein folding and its histone binding capability. In addition, we recently found that UHRF1 could be a target of PIP4K2B signalling, and others showed UHRF1 gene expression is dependent by YAP/TEAD binding to its promoter (43, 45). Our findings indicate that UHRF1 is targeted by PIP4K2B at post-transcriptional level.…”

“…Remarkably, UHRF1 protein downregulation was found also in cells seeded on soft substrates, perfectly matching the behavior of PIP4K2B in the same conditions (Supplementary Figure 6B). We recently proposed UHRF1 as a possible target of PIP4K2B signalling, while others showed that its function is tightly connected to its binding to PtdIns5P (43, 44). In addition, UHRF1 gene has been identified as a target of YAP/TEAD transcription factors (45).…”

“…plasmids. Lentiviral particles were produced as described here (43). Briefly, 3×10 6 HEK293T cells were transfected with pLKO_1 (encoding sh_RNAi) or pCMV6-AC (Origene #RG217766, encoding GFP-UHRF1) lentiviral plasmids, together with psPax2 and pMDG2 vectors with a ratio of 4μg:2μg:1μg.…”

Prognostic Value of Long Noncoding RNA DLEU2 and Its Relationship with Immune Infiltration in Kidney Renal Clear Cell Carcinoma and Liver Hepatocellular Carcinoma

“… 12 It has been previously reported that T cells play an important role in immune regulation in the tumour microenvironment, such as the recruitment of regulatory T cells (Tregs) in the immune microenvironment by limiting the signal transduction of effector T cells and their killing effect on tumour cells. 35 Yang et al reported that a high proportion of DC cells and Treg cells and T cell exhaustion promote the tumour microenvironment in bladder cancer. 36 Our results also show that the expression of DLEU2 was associated with immune markers of CD8+ T cells, Tfh cells, Th1 cells, and Th2 cells.…”

“…Tregs can limit the immune system’s immunity to tumours and increase the body’s immune tolerance to tumours, leading to the immune escape of tumours. 35 DCs can lead to tumour immunosuppression and promote tumour growth and metastasis by increasing Tregs and activating CD8+ T cells. 37 Moreover, M2 tumour-associated macrophages can increase the activity of tumour cells and mediate the EMT process in tumours.…”